Unloader for compressors



May 23, 1933. v BUEHLER, JR 1,911,105

UNLOADER FOR COMPRESSQRS Filed Nov. 14, 1930 L007? Buelzler, Jr:

attain;

gwuento'o Patented May 23, 1933 UNITED STATES PATENT OFFICE LEON BUEHLER, JR., OF 'WAYNESBORO, PENNSYLVANIA, ASSIGNOR TO ERICK COMPANY, OF WAYNESBORO, PENNSYLVANIA, A. CORPORATION OF PENNSYLVANIA UNLOADEIR FOR COMPRESSORS Application filed November 14, 1930. Serial No. 495,765.

While the invention is not limited in its use,

it is designed primarily for use in refrigerating plants in which the compressors operate in a closed cycle.

Referring to the accompanying drawing, which is made a part hereof and on which similar reference characters indicate similar parts,

Figure 1 is a view in elevation of a conventional compressor showing the by-pass valve and its operating mechanism in section, and

Figure 2, a diagrammatic view of the operating system.

In the drawing numeral 10 indicates a compressor of any kind desired which is driven by means of an electric motor 11, the

motor 11 being started by means of lines 20 and 12. 13 and 14 indicate suction and discharge ports respectively to the compressor, the discharge port 14 having a check valve 15 therein. On the opposite side of the compressor are positioned intake and discharge ports 16 and 17 respectively. The discharge port 17 connects with the intake port 16 through a by-pass Valve 18. The valve 18 may be any suitable valve and may be operated in any suitable way. ,As here shown it is connected to a valve stem 19 which has a piston 21 on its upper end which piston operates in a cylinder 22. A cap 23 is positioned in the upper end of the cylinder 22 and secures a compression spring 24 which is positioned between the cap and the upper side of the piston 21. The cap 23 may be vertically adjusted in any suit-able way to vary the tension of the spring 24 to regulate the pressure required to lift piston 21. The cylinder 22 is provided with a port 25 for drawing ofl any pressure fluid which may leak past piston 21. The by-pass valve is so positioned as to be opened when the piston 21 is raised and when opened pressure fluid from the discharge side of the compressor is returned to the intake of the compressor to relieve the compressor of its load. Means for holding the by-pass valve open until compressor has come to maximum speed will now be described. As shown in Figure 2 there is provided a pump 26 having a discharge line 27 connected to a port 28 for delivering pressure fluid beneath the piston 21. The intake to the pump 26 is indicated at 29. Branch pipe 30 may enter the pipe 29 from a water jacket surrounding the compressor 10. Pump 26 is driven by an electric motor 31. A pressure operated switch 32 is connected through a pipe 33 with the discharge line 27. The switch 32 is set so as to close a circuit through lines 34 and 35 only when the pressure from the discharge of the pumphas reached a predetermined maximum. This will be the pressure at which the piston 21 is in its most elevated position and at which the by-pass valve 18 is opened. 36 indicates a switch which may be operated by a push button or by a thermostat, as desired. 37 and 38 indicate main electrical supply lines. At 39 is shown a switch for closing circuit through lines 40 and 41 and through coil 42 which when energized holds the switch 39 closed and which when de-energized allows the switch 39 automatically to open. A similar switch is shown at 43 which is opened when the field coil 44 has been suitably energized. The coil 44 is so designed as to be energized only when the main motor 11 has reached approximately its maximum speed. 45 denotes a pressure by-pass valve connecting the discharge line 27 with a waste line 46.

The motor 11 and the means for controlling the current thereto may be of any type desired, that shown being merely diagrammatic. For example, and preferably, the motor 11 may be started by any ush button type of switch which is operated when the lines 12 and 20 are energized. The re lay 44 and switch 43 are also shown diagrammatically. This switch is any switch which is operated when the motor 11 comes to approximately full speed.

In ope 'ation, the switch 36 is closed, This may either be manually closed or as indicated it may be closed by a thermostat control so as to start automatic operation of the system. When this switch is closed the motor 31 is started, to drive the pump 26 to build up pressure beneath the piston 21,- to'raise this piston and to open the by pass valve 18. \Vhen the pressure in the discharge side of the pump has reached approximately its maximum, the switch 32 is closed to close circuit through the line 38, switch 36,.line 34, line 12, motor 11, line 20, switch 32, line 35, coil 42 to line 37. This energizes coil 42 and closes the switch 39 so that the circuit now travels through the line 40 and .41 to the line 37 independent of the switch 32. As soon as switch 32 is closed the main motor 11 starts operation of the compressor. Since the pump 26 is still in full operation, the by-pass valve 18 is opened so that the compressor 10 operates without any load. As the motor 11 comes to its maximum speed the coil 44 becomes energized to open the switch 43. The pump 26 therefore stops and the pressure is relieved beneath the piston 21. Fluid therefore may leak back through the pump and allow the valve 18 to close. therefore is closed so that the compressor operates to draw fluid through the line 13 and discharge it through 14 into the high pressure line of the compressor system. hen the pressure of the pump drops, the switch 32 will again open but since the circuit is now closed through switch 39 the system will continue to operate with the switch 32 open. Opening switch 36 serves to stop the motor 11. As soon as the motor 11 is stopped the switch -13 automatically closes so that all parts will be in position to operate again when the switch 36 is again closed.

While the pressures in the discharge port 17 and suction port 16 have been described as substantially equal when the by-pass valve 18 is open it is of course well understood that there will be a pressure difference. The size of the by-pass valve 18 will determine somewhat the degree of difference in pressure. For all practical purposes there will be no load on the pump when the valve 18 is open.

It will be obvious to those skilled in the art that various changes may be made in my device without departing from the spirit of the invention and therefore I do not limit myself to what is shown in the drawing and described in the specification, but only as indicated in the appended claims.

Having thus fully described my said in- The by pass valve 18 vention, what I claim as new and desire to secure by Letters Patent, is:

1. Means for reducing the starting torque of compressors which comprises a fluid passage connecting the discharge and the suction sides of the compressor, a valve in said passage, .means operable independently of the compressor, for holding said valve open during the starting of the compressor, said means being stopped as the compressor reaches approximately operating speed, substantially, as set forth.

2. An unloader device for a compressor comprising an equalizing line between the discharge and the suction of the compressor, a valve in said line, an auxiliary compressor, a cylinder having a piston therein connected with the said valve, a connection from the discharge line of the auxiliary compressor with said cylinder whereby operation of said auxiliary compressor will cause the said valve to open the said equalizing line, means operating when the compressor is substantially up to speed for stopping the said auxiliary compressor, substantially as set forth.

3. In combination a fluid compressor, a motor for operating said compressor, an equalizing line connecting the discharge with the suction of the compressor, a by-pass valve in said line, a secondary compressor, means whereby the discharge from the secondary compressor will operate the said bypass valve toopen the same, a switch operated by the pressure developed by the secondary compressor, said switch controlling operation of the main compressor when the pressure developed by the secondary compressor has reached a predetermined point, substantially as set forth.

4. In combination a fluid compressor, a motor for operating said compressor, an equalizing line connecting the discharge with the suction of the compressor, a by-pass valve in said line, a secondary compressor, means whereby the discharge from the secondary compressor will operate the said bypass valve, a switch operated by the pressure developed by the secondary com ressor, said switch controlling operation 0 the main compressor when the pressure developed by the secondary compressor has reached a predetermined point, and means whereby the secondary compressor will be stopped from operating when the main compressor has reached approximately its operating speed, substantially as set forth.

5. An unloader for compressors comprising a fluid operated by-pass valve positioned in a passage connecting the discharge with the intake side of the compressor, auxiliary means for supplying fluid pressure for holding said valve open during the starting of the compressor, and fluid pressure means for stopping flow of fluid pressure as soon as the compressor has reached approximately maximum operating speed, substantially as set forth.

6. An unloader for compressors comprising the combination of an equalizing line between suction and discharge of the compressor, of a Valve in said line, a cylinder, a piston in said cylinder, said piston being operatively connected to the said Valve, and auxiliary fluid pressure means for operating said piston, said means operating to open the Valve and maintain it open until the compressor has reached substantially maximum operating speed, substantially as set forth.

In Witness whereof, I have hereunto set my hand at Waynesboro, Pennsylvania this 8th day of November, nineteen hundred and thirty.

LEON BUEHLER, JR. 

